Updated Spring 2009
SUMMARY & OBJECTIVES CHAPTER 23 – ECOLOGY, THE ENVIRONMENT, AND US
Summary
1. The earth is a closed system. Energy (from the sun) is the only input and is captured by producers
(photosynthesis).
2. Living organisms are connected through food webs made of producers and consumers.
3. Energy gets “lost” as it moves up trophic levels from producers to tertiary consumers. It is lost through
cellular respiration, growth, reproduction, excretion, and defecation.
4. Biological magnification causes nondegradable (sometimes harmful such as mercury) chemicals to be
more concentrated in organisms as it passes along the trophic levels.
5. Considering problems facing the world such as world hunger, global warming, and water resources, a
vegetarian diet is a more “efficient” use of energy.
6. There are natural cycles that ensure that materials move from living to nonliving systems: the water
cycle, the carbon cycle, and the nitrogen cycle are examples.
7. Humans can upset the cycles with actions. Water pollution and global warming are examples of human
activity altering the chemical cycles.
Objectives
1. Describe how energy moves through trophic levels and how it is lost as it moves up trophic levels.
2. Describe where humans fall in the trophic levels.
3. Describe how biological magnification can affect human and other living organisms’ health.
4. Describe a few benefits of eating a vegetarian diet, or eating less meat.
5. Briefly describe the carbon cycle.
6. Describe how global warming is caused by a disruption in the carbon cycle caused by humans.
7. Discuss some of the current environmental concerns and approaches to “fix” them.
Key terms:
Producer, primary consumer, secondary consumer, tertiary consumer, biological magnification, trophic
level, carbon cycle, carbon dioxide, global warming, sustainability
SUMMARY & OBJECTIVES CHAPTER 24 – HUMAN POPULATION, LIMITED
RESOURCES, AND POLLUTION
Summary
1. The global human population is altered by birth rate and death rate.
2. Human population has increased exponentially in the past 200+ years primarily due do a decrease in
death rate.
3. The age structure of a population can predict its future growth rate.
4. Carrying capacity is the population maximum for a particular environment. We may be reaching the
earth’s carrying capacity for humans.
5. The increase in human population has lead to an increased human impact on earth such as causing
pollution, soil erosion, deforestation, and reducing biodiversity. We need to reassess our actions and
strive to live sustainably.
Objectives
1. Describe how human population has changed over time and how age structure affects future growth
rates.
2. Define carrying capacity and relate it to human population.
3. Describe ways that humans can minimize their impact on the earth and strive for sustainability.
Key terms
birth rate, death rate, exponential growth, carrying capacity, sustainability
